Part b and e.
Flux = surface integral of B (dot) ds
The Attempt at a Solution
I just want to make sure that I have a good understanding of ds. ds is just the direction of the vector that is normal to our area that we are finding our flux throuhg correct? so that is why in part A we just take B*A in the -z(hat) direction because that is the direction of our ds vector. But for part b we have to find our flux in terms of the angle theta and I am stuck with how to find ds. what I have written down at the bottom there for ds is what the what it should be supposedly, but I can't see where it came from and I am struggling to derive it. How do I get ds here in terms of theta?